The present invention relates to devices used for measuring and monitoring the female cervix and pelvis in the field of Medical Obstetrics.
The assessment of the cervix during pregnancy, labor and delivery is an important part of Obstetrical monitoring. This measurement can affect whether the patient is considered ready for delivery or is sent home with a diagnosis of false labor. Still, labor and delivery room personnel generally continue to rely on blind palpatory estimations for measurements of cervical dilation.
In practice, a person intending to perform a cervical measurement places a sterile glove on their hand, and extends their index and middle fingers into the patient's vagina. Once the cervix is palpated, the cervical os is located with the examining finger tips which are spread apart or abducted. The degree of opening of the cervical os is usually blindly assessed merely by the spacing between the index and middle fingers.
The generally accepted scale ranges from zero to ten (centimeters or points). This form of cervical monitoring is based purely on a sense of feel without any visual aspect. A finding of cervical dilation of less than three centimeters may warrant the physician to send the pregnant patient home. Should the clinician estimate a cervical measurement of greater than three centimeters, the patient is usually diagnosed as being in labor, and routinely is monitored through the completion of delivery. Throughout this monitoring period, the patient may receive several more manual cervical exams to evaluate the progression of labor. When the patient is measured to be ten centimeters or greater, she is diagnosed as having complete cervical dilation, and then is encouraged to push the baby out. Prior to the attainment of a completely dilated cervical measurement, patients are encouraged not to push yet, for risk of premature delivery and harm to both mother and baby.
It is apparent that the cervical measurement is of critical importance in diagnosing labor, yet using current practices there is a large potential for subjective variation and error. As cervical dilation is in essence simply measured by feel, a cervical and pelvic birth canal examination and measurement could vary greatly, depending upon the level of experience, knowledge and skill of the examiner. If the cervical dilation is measured inaccurately, the patient may potentially be misdiagnosed, and be subject to improper care.
During the initial evaluation of a pregnant patient there are several important measurements that must be obtained to ensure a normal delivery. This includes the measurement of the pelvic conjugate diameter, a sizing estimation used to determine the size adequacy of the mother's pelvic canal for a normal vaginal delivery. This again is roughly estimated manually during the sterile glove exam, by using the length of the index finger to measure the distance between the posterior coccyx and anterior pubic ramous. Should pelvic inadequacy be determined during this exam (i.e., the mother's canal is too small or the baby too large) an elective Cesarean section may be planned. This measurement, if performed more accurately and reliably, could potentially avoid improper early decisions pertaining to the pregnancy.
Although various devices have been proposed for more reliably measuring cervical dilation, none have achieved widespread acceptance apparently due to their cost, complexity and inconvenience. For example, most devices have been cumbersome and difficult to read during normal field conditions, and generally considered inoperable during darkened field conditions. Accordingly, there is a need for a more accurate means of cervical and gravid pelvic examination, that produces objective, visually interpreted measurements of the cervix and pelvic birth canal as may be desired during pregnancy, labor and delivery.